Page 49 - eProceeding - IRSTC & RESPEX 2017

Khairun Nizam b Sa’adan/ JOJAPS – JOURNAL ONLINE JARINGAN COT POLIPD

3.5.1 Accumulation of Heavy Metal inside sludge after 55 days experiment

The scanning electron microscope (SEM) images below in Figure 7 were analyzed before and after experiments. The SEM shows
accumulation of heavy metal on the sludge cross section. Figure 8 showed the result of EDX associated with the SEM. The EDX
analysis showed the agglomerates contained of Zinc and Cu with others accumulation type of heavy metals presents in the sludge.

(i) Cross-section of the sludge before operation (ii) Cross-section of the sludge with heavy metals
accumulation after operation.

Figure 7: Scanning Electron microscope (SEM) of sludge after 55 days of experiments

(ii) EDX analysis show the presence of Zn and Cu inside
(i) EDX point shoot images
the sludge

Figure 8 Energy Dispersed Extra (EDX) analysis after 55 days of operation

3.6 Biogas Production
The biogas production was symbolized based on volume production (mL) as given in Figure 9. Basically the biogas comprise
of 60% of methane (CH 4 ) and 40% of carbon dioxide (CO 2 ) in the anaerobic digestion, but however, the methane content varies
with type of feedstock used because each substrates has different composition (Siripong and Dulyakasem, 2012). The
effectiveness of the anaerobic digestion can be determined from pH value, % COD removal and gas production. Gas production
can be useful indicator in observing reactor suffering from toxicants.
During the first occasions for single anaerobic digestion of AWW sample, the gas production decreased over the time. Gas
production can be useful indicator in observing reactor suffering from toxicants. Considering to the previous study from Zayed
(2000), it was assumed that the presence of heavy metal concentrations in AWW during mono digestion might have cause
inhibition in the reactor performance. Accumulation of heavy metals may indicate by reduced level in gas production and biogas
methane content (Yue et al., 2013). Low pH value observed in the phase also believed to yield for low optimal performance of
methanogens in gas generation. In relation to the situation, COD removal were erratic with average removal during the digestion
was 63.4% and gas production yield at day 29 was only 5ml and there was no methane achieved. These results showed that
anaerobic digestion with AWW has proved difficult and the reactor was operating under unstable condition. The gas composition
produced during this phase was compose of N 2 (74.04%), O 2 (24.60) and CO 2 (1.36%). The high percentage of nitrogen in the
reactor indicates that denitrification was the main biological process yield in the system during this phases (Bernet et al., 2000).
Denitrification is a process in which nitrate is reduced to nitrogen gas by facultative anaerobic bacterium (Akkunna et al., 1992).

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